1. Field of the invention.
The present invention relates to an improved rotary seal and energizer with pressure balancing and improved lubrication properties.
2. Description of the related art.
Prior seals have limitations when given an applied pressure and relative velocity, i.e., when a sealed rod is rotated. In operation, typical pressure applications occur at 3000 PSI and above, and fairly low surface velocity movement of 10 to 50 feet per minute.
Due to the rotary motion and poor lubrication, the constant friction can lead to heat generation increases, thereby accelerating wear and causing seal extrusion and loss of material. During seal pressurization, the seal slides over in the groove and the energizer forms up in a corner creating a heavy load, resulting in high friction. This high friction accelerates heat generation, compression set, and possible loss of seal ring energization, which may also result in the creation of an undesirable dynamic interface created between the energizer and seal ring, thus producing undesirable abrasion and wear to the energizer.
To improve those situations, the present invention includes a pressure balance design which reduces overall friction during operation and improves the lubrication underneath the seal ring. Preliminary results indicate a reduction of torque of over fifty percent. Heat generation is also reduced by nearly fifty percent and an improved leakage control is also evident.
The seal ring of the present invention includes a lower center groove. The center groove is in the contact space between the seal ring and rod. The groove minimizes the bottom contact area, thus increasing the contact stresses and improving leakage control. When the system is pressurized, the seal ring pivots about a point on the bottom surface contact area, thereby providing a pressurized seal contact along a larger bottom contact area, while maintaining an extrusion resistant chamfer.
In the invention, a seal for sealing a gap between a first member and a second member moving relative to the first member comprises a ring with a cross section, the cross section having a pivot point and a perimeter. When external pressure is applied to the ring, for instance with the addition of fluid pressure, the ring responds by rotating about the pivot point.
In another embodiment of the invention, a seal arrangement is provided for sealing a gap between a first member and a second member, the second member moving relative to the first member, the seal arrangement comprising a first ring and a second ring. In this embodiment, the first ring has a cross section with a perimeter and a pivot point, the first ring pivoting about the pivot point when external pressure is applied. Additionally, a second ring is provided with a cross section and a perimeter.
In yet another embodiment of the invention, a seal for sealing a gap between a first member and a second member moving relative to the first member includes a ring having first surface and a second surface, the second surface sealingly engaging with the second member when the seal is subjected to external forces, and the second surface disengaging with the second member when the external forces are absent.
In a further embodiment of the invention, the seal arrangement comprises a first ring having a cross section with a perimeter, a first lip, a second lip, and a recess defined between the first lip and the second lip. Additionally, a second ring is provided and disposed between the first member and the first ring, the second ring having a perimeter that protrudes into the recess of the first ring during a pressurized state, and spans the recess during a non-pressurized state.
In an alternative embodiment of the invention, a sealing structure for sealing a gap between two machine parts arranged for motion relative to each other comprises a sealing ring having an inner surface facing the second machine part, the inner surface having a pivot point, a first lip, a second lip, a recess defined between the first and second lip, and an outer surface facing toward the first machine part, the sealing ring pivoting about the pivot point when exposed to external pressure. Additionally, an energizer ring is provided having a cross section with a perimeter, the energizer ring being disposed between the outer surface and the first machine part.
Yet another embodiment of the invention can be described as a method of sealing a gap between a first member and a second member, the second member moving relative to the first member, the method comprising the step of providing a ring capable of pivoting about a cross sectional point when subjected to external pressure.
The present invention is advantageous over the prior art seals in that it provides a sealing surface that increases in surface area as pressure against the seal escalates, while providing a high contact pressure profile at the sealing apex to improve leakage control. The increased sealing surface is accomplished by the rotation of the seal member during pressurized states, thereby placing a larger part of the seal in contact with a machine part when most needed.
It is a further advantage of the present invention that a reduced sealing surface is provided during low pressure operation. When the seal is in a low pressure state, and rotation about a pivot point has not yet occurred, the present invention advantageously provides a recess along its sealing surface, thereby reducing the amount of friction between the machine part and the seal.
It is yet another advantage of the present invention that a tapered wall is provided on a side of the seal, the tapered wall serving to firmly hold the seal in an ideal location against a surface of the seal housing once the seal has rotated about the pivot point.
It is a further advantage of the present invention that a recess is provided on the top surface of the seal, for interaction with an energizer ring. By providing a recess, ridge, bump, or other means of increasing surface area and simultaneously introducing localized high stresses, facing the energizer ring, the edges of the seal""s recess transmit deforming pressure to the surface of the energizer ring during a pressurized state, thereby greatly increasing the coefficient of friction and/or the contact surface area, and consequently substantially eliminating a dynamic interface between the energizer ring and the seal.